There are continuing efforts to develop new and improved load bearing assemblies. In general, the primary objectives of these efforts are to obtain a durable and inexpensive load bearing surface that is relatively easy to manufacture. It is also important to address issues in the attachment of the load bearing surface to the support structure.
It is known to provide molded load bearing surfaces for a wide variety of applications. For example, molded plastic chairs (e.g. lawn chairs) are available from a variety of well known suppliers. Although these molded chairs provide an inexpensive seating option, they typically do not provide the level of support and comfort available in more expensive load bearing surfaces, such as conventional cushion sets. Rather, they provide an essentially linear force/deflection profile, which gives the typical molded seating surface the feel of a drum or a trampoline. In seating and other body-support applications, this may result in an uncomfortable and sometimes ergonomically unacceptable load bearing surface. Further, the ability to tune the characteristics of a conventional molded seat is relatively limited. Different materials and different material thicknesses can be used to provide a limited degree of control over the characteristics of the seat, but this level of control is not sufficient in many applications. In many cases, materials that are thick enough to provide the necessary support are too rigid and uncomfortable, and thinner plastic surfaces, such as membranes or woven plastic fibers tend to permanently deform (or creep) over time.
Recently, as disclosed and described in U.S. Patent Application Publication No. 2006/0267258, filed Jun. 12, 2006, titled “Load Bearing Surface,” the subject matter of which is incorporated herein by reference, it has become known to make a strong, yet flexible and comfortable load bearing surface using a molded elastomeric membrane. The molded elastomeric membrane may be decoupled between a first direction and a second direction, by mechanical structure, by orienting the membrane to align the crystalline structure of the elastomeric material in one direction or by some combination of the foregoing. The decoupled elastomeric material exhibits support characteristics that are particularly well suited for use in seating applications because it provides different degrees of support in different directions. Further, by increasing the alignment of the crystalline structure of the elastomeric material, the level of creep in the membrane can be dramatically reduced.
There continues to be a desire, however, for improvements in the attachment of elastomeric load bearing surfaces, and particularly molded elastomeric load bearing surfaces, to a support structure. Of course, screws and other separate fasteners can be used, but they are known to be problematic because of the extra costs associated with additional materials and manufacturing steps, and because they tend to be unattractive. One known method that eliminates the use of separate fasteners includes molding a plurality of receptacle holes in the load bearing surface that align with protrusions on the support frame to snap-fit the elastomeric load bearing surface to the support frame. Another known method includes molding a peripheral portion of the lead bearing surface in situ with a portion of the support frame. Although generally acceptable, these methods can be problematic in situations where the features of the support frame cannot be manipulated as necessary to accommodate or receive attachment features on the load bearing surface. For instance, it can be difficult and costly to create a steel support frame with a plurality of properly spaced apart protrusions extending from it to attach to a load bearing surface.